The role (relationship) of visual and motor imagery in estimating reach

The primary intent of this study was to explore fundamental questions about the role and relationship between motor (MI) and visual (VI) imagery within the context of estimating reach. Experiment 1 examined and compared VI and MI tasks under matched environmental conditions with the intent to explore the distinction and cooperation of the visual and motor systems in representing actions. The design of this experiment included an interference paradigm modified from Stevens (2005) in which six blocks of trials (conditions) were used: MI, VI, MI with visual interference, MI with motor interference, VI with motor interference, and VI with visual interference. Results indicated that MI was significantly more accurate than VI in regard to total error, distribution of error and mean bias (p <= .05). Significant increases in the number of errors and estimation bias were found when the modalities for the imagined task and the interference task were matched. The data showed that motor tasks interfered with the ability to MI, whereas visual tasks interfered with the ability to VI. Experiment 2 included a response-delay paradigm modified from Bradshaw and Watt (2002) in which eight blocks of trials were used: MI and VI conditions with no-delay and delays of 1-, 2- and 4 s. Overall, this experiment demonstrated that response-delay influenced accuracy of the MI (visuomotor) task, but not the VI (perceptual) task. That is, after a 4s delay, error in MI increased significantly. Interestingly, these results may indicate a crucial temporal constraint for the representation of distance, isolated in the visuomotor system. In view of both experiments, the findings are consistent with the notion of a distinction between vision for perception (VI) and vision for action (MI) as advanced by Goodale, Westwood & Milner (2004). In conclusion, VI seems to delineate relevant spatial parameters within the environment and then transfer the information to MI. At this point, information is computed in terms of biomechanical possibilities for a certain movement. In summary, just as perception and action are firmly linked, so too are MI and VI.